For the reason: this is a template (with at least 25 UI contros) that normally needs Model A as datatype. the DataTemplate is a ListvVewItemTemplate. But the datatype can be of type Model B. Model B has a property called 'Model', which is of type Model A.
So instead of copy pasting the whole block template and use style triggers or DataTemplate selectors, I just want to change the DataContext (from "{Binding}" to "{Binding Model}")

anyone has some suggestions, a solution?

Thx!

EDIT: the Converter returns the type of the incoming value (the data object itself). that way i can know when Model B is using the template and so to change the DataContext.